Q: For digestive reasons, I have been drinking soymilk instead of cow milk, but someone told me that soy depletes my calcium. Is that true?
-- Heather, Salt Lake City, UT

A: All protein -- whether it comes from animals (poultry, fish, meat, eggs, and dairy foods) or plants (mainly soy and nuts) -- gradually depletes your calcium. That's why you need 600 milligrams of calcium twice a day. That said, most soymilk comes fortified with calcium and vitamin D -- just make sure yours is. And shake it well before pouring; there's some evidence that the calcium gradually settles on the bottom.

Q: What's the difference between steel-cut oats and the oat flakes used in quick-cooking oatmeal? Do the flakes contain enough fiber to be used in breakfast smoothies?
-- Elena, New York, NY

A: Both kinds of oats have considerable fiber (read the label, as the amount varies from brand to brand), and both can be used in breakfast smoothies. But here's why we're fans of steel-cut oats: The finer the oats are cut, the faster your body absorbs them, and the more they make your blood sugar spike. With flakes, you get speedy absorption and sharper spikes. Steel-cut oats take much longer to absorb. But if adding fiber to breakfast smoothies is your number one concern, neither is as good as a teaspoon or so of powdered psyllium husks. You can also try adding leafy greens to those smoothies; balance their flavor by adding sweet apples as well.

Q: I'm a vegetarian, and I often make enough food for more than one meal. When I refrigerate the leftovers, how long do they retain their nutrients? If I prepare a dish one evening, will the vegetables still be nutritious the next night?
-- Lana, Limassol, Cyprus

A: There data on this is sparse, but overnight storage in a refrigerator doesn't seem to affect nutrient value much. Cooking, however, reduces some nutrients (though not all; it actually increases lycopene). As a general rule, it's usually better to steam veggies rather than boil them. If you boil broccoli, for instance, there is a 66% nutrient loss into the boiled water, so opt for lightly steaming it.

Some good guidelines:

• The less water you use to cook produce, the more nutrients it retains.
• The lower the temperature you use, the more nutrients you get to eat.
• Refrigerating food overnight seems to maintain most nutrients pretty well -- perhaps better than freezing it.

Q: Which is better: whole-wheat or whole-grain products? You recommend whole grains to help shrink belly fat. What's the difference?
-- Patty, Puyallup, WA

A:  There is no difference. Whole wheat IS a whole grain. "Grain" is the generic category; wheat is a type of grain. When you get 100% whole wheat, you are getting 100% whole grains. When you get 100% whole grains, you could be getting wheat, rye, barley, oats, etc. It's the phrase "100% whole" that's essential. If the label only says "wheat flour," you're probably not getting 100% whole wheat.

And yes, any whole grain will help you shrink belly fat. Partly because its high-fiber content curbs your appetite. Aim to eat 8 to12 grams of fiber at each meal, especially at breakfast and lunch -- it decreases late afternoon and evening munchies.

Q: Is the soft-serve frozen yogurt you get at frozen-yogurt shops as good for you as regular yogurt?
-- Terry, Poway, CA

A: Unfortunately, no. Frozen yogurt tends not to have live cultures that help with digestion (known as probiotics). In addition, frozen yogurt usually has much more sugar, less protein, and more fat than true yogurt. Want a great frozen dessert? Freeze some fruit, especially grapes and peeled bananas, and enjoy them right out of the freezer. Or put the frozen fruit directly in a juicer (thanks to healthy-eating expert Ann Crile Esselstyn for that tip) and you'll get a cool, healthy way to end a meal.

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